Theodok kortkaueil



Jan. 27, 1931.

T. KORTHAUER 1,790,382

TELEPHONE SYSTEM Filed Oct. 25-. 1929 IHVENTOR 1 Theodor Karl/mus! Patented Jan. 27, 1931 Urn srA ss PATENT oFFics 'rnnonon iron'rnzinnn, or nnnmnsinninivssranr, GER ANY, ASSIGNOR, .B Y MESNE ASSIGNMENTS, 're Airnnrcnn rnnnrnonn Ann TELEGRAPH COMPANY, A con- PORATION OF NEW YORK I I TELEPHONE sYsrnM Application filed October 23, 1929, seal a... 401,849, and in Germa y iMaylG, 1928.

This invention relates to electric telephone systems and is more particularly'concerned with such systems, automatic in character, in which one idle line of a number of available connecting lines is automatically 'se lected, upon the initiation of a call bya subscriber. The main object of this invention consists in enabling the determination of the particular line selected, byIan automatic selecting device.

In many cases, it is for specific reasons, to determine which one of a plurality or a group of connecting lines,

rates for telephone conversations, it is necessary for the operator tolknow which one of va group of available connecting lines has been picked out by an automatic selector switch, in order to enable her to check up the completion of a desired call. .F or instance, this is the case where existing local automatic exchanges may be connected with each other by a distant exchange served by an operator. v

In accordance with this invention, it is made possible to indicate the seizure of a, connecting line, picked out from a group of available connecting lines, in that 'definte simple signals are provided, showing the specific line selected for the connection. In

accordancewith the preferred embodiment of theinvention, a switching mechanism is operated upon initiation of a call by a calling subscriber, after seizure of an idle line, selected from a group of available connecting lines. This switching mechanism is operated in such a manner that the calling subscriber, or the'operator at the exchange, readily recognizes the specific line selected.

he invention will become more clear'as the following detailed description proceeds,

desirable, or required,

illustrative examples of the fundamental inventive idea andw-hich, it should be understood, are, by no means, intended to have the effect of limiting the interpretation of the invention, short of its broad and most comprehensive scope, as expressed in the appended claims. Figure 1 shows a circuit diagram of an automatic telephone system, in which the idea of my invention is embodied. Figure'Q is a similar diagram, for obtaining thesame object in a modified manner. Similar reference characters refer to similar elements in both figures of the drawing.

In the diagrams of the drawings, relay windings and contacts operated by the same, are designated by co-ordinate characters, the windings being marked by capital characters and the corresponding contacts by smallchara cte'rs. The terms resting contact and working contact are used in the following description, the former meaning the conditionioii a relay contact in its die-energized condition andthe latter meaning the condition of a relay contact in its energized condition. 7 V

According to both examples shown by the two figures of the drawings, an idle connecting'line is picked out, by means of a pre-se lector switch, (also called line switch) from an available group of identical' such connect- Ground, operating battery, winding I 01": re 'lay It, resting contact 1t, connecting line a1,

subscriber loop Tn, connecting line'bl, resting contact 2t, winding II of relay B, back to ground.

Thus, relay R is energized and connects, by operation of its associated contacts, the following circuits otthe pre-selector V. Ground, interrupter U, winding D 'of rotary operating magnet, resting contact 36, working contact 47Wl1lCl1 has been operated because of the energiZat-ion of the relay R upon initiation of the subscribers call-contact 0, switch arm 5, battery, back to ground.

The pro-selector V. \V. is advanced by one step and, accordingly, the following circuit for the rotary magnet I) is established Ground, interrupt er U, winding of rotary magnet D, resting contact 32:, contact bank 1-l0, switch arm 5, battery, back to ground.

The rotary magnet D will further advance the pro-selector V. until it reaches an idle line from the group of available connecting lines. Assuming that such idle line has been found, the following circuit will be established: Ground, battery, contact arm 5, contact bank 1l0, working contact 4r, windings II and I of relay T, test line 01, switch arm C of pro-selector V. WY, windings I and ll of relay G, back to ground.

By the establishment of this circuit, relays T and C will be energized. Contacts 1t, 22? and 375, associated 'ith the relay T, will, accordingly, be operated. By such operation of contacts 1t and 225, the subscribing station Tn will be connected with the idle line selected by the pre-selector from the group of connecting lines. The circuit for the relay It will, accordingly, be interrupted and the relay become de-energized. *Furthennore, the relay C is energized by the establishment of the above mentioned circuit and will open its contact 50, thus inserting winding of the relay C, which has a high ohmic resistance, into the circuit of the relays C and T. By the operation of the contact 32?, associated with the relay T, the winding II of the relay T will be disconnected from the above described circuit. The circuit for the relays C and T will then be as follows: Ground, battery, contact arm 5, contact bank 1l0, working contact 3t, winding I of relay T, test line cl, switch arm 0 of pre-selector V. windings I and II of relay C, back to ground. In accordance with this invention, the pre-selector V. V. is provided with a fourth contact bank, besides the usual three contact banks, two of which (switch arms a and 1)) Serve for the connection of the two operating lines (a1 and b1) and the third of which (switch arm 0) serves for control and testpurposes.

Resistances lVi, of dill'erent values, are in-. sorted in the connections to the contacts of the fourth contact bank, the diiiferent resistance values corresponding to the-individual connecting lines. An ammeter M is arranged at the subscriber station, or also at the exchange, to be observed by the subscriber, or by the operator. Whenever an idle line of the available group of connecting lines is seized by the pre-selector V. a current circuit for the ammeter M will be closed, which includes a resistance co-ordinated to the specific line which has been selected. The trace of the current, in accordance with Figare 1 for this circuit, is as follows: Ground, to battery, resistance VVZ', switch arm d, line (Z1, ammeter M, back to ground.

The ammeter will show a definite deviation, depending on the value of the resistance U, in accordance with the individual line of the available group of connecting lines picked out by the pre-selector V. N. The calling subscriber, or the operator, may, thus, easily and immediately observe over which line of the connecting lines the connection has been made. In case the ammeter is arranged the subscriber station, the subscriber may a gise the operator of the specific line selected by the pre-selector, or, in case the amineter M is arranged at the operators end, the operator, herself, may observe which of the connecting lines has been picked out. The am'meter will be energized during the entire period of conversation and, thus, apprise the operator, or any other control person, at all times, of the real trace of the connection from the calling subscriber to the called subscriber and, thus, enable her to enter into the connection and control the final completion of a desired call. The calibration of the ammeter scale may be made such that it directly indicates the number, or any other marking of the line which has been selected.

Whenever the calling subscriber Tn is connected to an idle line of the group of available connecting lines, he may proceed to make his call, for instance, by transmitting a definite number of current impulses, by means of his dialing device, or he may have the operator make the connection manually. The relay J, across which the calling subscriber receives its supply current, will then be energized through the following circuit: Ground, battery, winding I of relay J, switch arm a of the pre-selector V. working contact 1t, connecting line a1, subscriber station Tn, connecting line ()1, working contact 22,, switch arm 6, winding II of relay J, back to ground.

With the energization of relay J, contacts Sj, and Gj will be operated. By the closing of the contact 87', a circuit is formed for a further relay V from ground to battery, the winding of relay V working contact 8;} back to ground. With the transmission of the selecting current impulses by the calling subscriber, the current impulses will be transferred by means of the relay J and the current impulse contact (Sj to the impulse current receiver. Thus, with the first release of the armature of relay J, the following circuit is formed for a further relay N: Ground, battery, winding of relay l l, resting contact 9 7', working contact 1001, back to ground.

During the period 01" impulse transmission, the relay V which is a relay with delayed action and, similarly, the relay N re main energized. Thus, the contact 7n, associated with the relay N, will short circuit a choke coil D1" during the impulse transmis not essential for an understanding of the novel feature of the present invention.

Furthermore, no description will be given of the final completion of the call, as this,;

also, has no bearing on the operation of the new additional device provided in accordancewith the invention.

Referring'to the clrcuit diagram of Fig ure 2, which represents a modified system of that shown by Figure 1, means are provided for indicating acoustically'the specific line of a group of available connecting lines,

selected upon initiation of a call-by a calling subscriber Tnl, instead of operating an optical signal, such as provided 1n accordance with the exemplification of the invention, illustrated by Figure 1. The subscriber V Tnl, upon the initiation of a call, is connected in the same manner as in Figure 1, with an idle line of an available group of connecting lines, by means of an automatic preselector, or line switch, as described. The operation of this pre-selector will not be dis- 2'; cussed, as this has been done with reference to Figure 1. Assuming that the calling subscriber T111 is connected with an idle line of the group of available'connecting llnes, the

following circuit for the relay J1'will-be formed: Ground, to battery, winding I of the relay J1, switch arm al of the pre-selector V. W. 1, connecting line a2, working contact 1t1, subscriber station Tnl, working contact 2251, connecting line 62, switch arm 61, winding 11 of relay J1, back to ground.

The relay J1 will be energized by this circuit and, by operation of its contact Sjl, will close a circuit for the relay V1, which circuit is traced from ground to battery to winding of the relay V1, working contact 871, back 7 to ground. Thus, the relay V1 responds and operates contacts 10411, 13021 and 1401. By

the closing of the contact 14 01, abuzzer U2 is inserted in the line 122 of the'subscribers line. Thus, the calling subscriber Tnl will receive a distinct signal, which will notify him over which of'the available. connecting lines he has been connected. A buzzer is co-ordinated to each one of the lines of the 3 group, whereby different announcements will be given to the subscriber. With the transmission of the calling current impulses of the subscriber T711, the relay J1 transfers the current impulses sent out by the subo scriber across the current impulse 6j1 contact to the subsequent current impulse receiver. With the first release of the relay J1 during the transmission of the current impulses, the following circuit :will be formed for the relay N1: ground, to'battery, winding of relayNl, resting contact 931, workingcontact 10c1, back to ground.

5 The relay V1 remains energized during the entire period ofthe current impulse transmission, for which purpose it is designed, as a relay with' delayed action and so is the relay N1. Through the responseof the latter relay N1, the contact 11n1 is closed, forming the following circuit for the relay H: Ground, to battery, winding of relay H, working contact 111L1, workingcontact 1301, back togroundp' The relay H and maintains itself in an energized condition, by'means of its own holding current cir cuit, closed over contact 12h;- By opening of the contact 15h, operated by therelay winding H, thebuzze'r U2 is disconnected. The relay'H remainsenergized during the entire period of the connection'and, simi larly, the relay V1, whereas the relay N1 becomes de-energized after the completion of the impulsecurrent transmission; -During the transmission of the impulse currents, the

choke coil Drl is short-circuited by means of contact 77b1, in orderto-improve the operation of the impulse transmission.

The further operatlons necessary for completlng a call and dissolving the same, after termination of a conversation, will not be de-' scribed, as they have no reference tothe ticed in many other ways, without departing from the sp rit and scope thereof, in attaining the objects, as hereinbefore set forth. 3

What I claim to be secured by Letters Patent in the United States is 1.. In. a telephone system, an automatic switch having brushes and contacts, a telephone. lineterminating in brushes of said switch, a group of trunks appearing in the contacts of said switch, means responsive to the initiation of a call at the substation of said line for setting said automatic switch in motion to select an idle trunk and to extend said line thereto, distinguishing elements, each individual to a different one of said trunks, means for connecting said elements through the brushes of said switch to said line, and signal means responsively controlled by said distinguishing elements for identifying the particular trunk to which said line is connected. 1

Y 2. In a telephone system, an automatic switch having brushes and contacts, a telephone line terminating in the brushes of said switch, a group of trunk circuits appearing in the contacts of said switch, means controlled overrsaid line for setting said switch in operation to select an idle trunk and to extend said line thereto, resistance elements,

is energized by this circuit each individual to one of said trunks, said elements differing from each other in order to distinguish said trunks, and an indicating meter connected to a brush of said switch and included in circuit with said resistance elements to give a visual indication identifying the particular trunk to which said iine is connected.

3. In a telephone system, an automatic switch having brushes and contacts, a telephone line terminating in the brushes of said switch, a group of trunks appearing in the contacts of said switch, means responsive to the initiation of a call at the substation of said line for setting said automatic switch in motion to select anidlc trunk and to extend the line thereto, tone producing devices, each differing from the other and respectively individual to said trunks, means for connecting said tone devices through the brushes of said switch to said telephone line, and means at the substation responsive to said tone producing devices for giving a signal identifying the particular trunk to which said'line is connected.

In testimony whereof I affix my signature.

THEODOR KORTHAUER. 

